1. Field of the Invention
This invention generally relates to an adapter for an optical instrument and in particular to an adapter that provides for a quick attachment and release of an eyepiece from a B-mount instrument.
2. Description of Related Art
Eyepieces are associated with a number of optical devices including, as examples, endoscopes and boroscopes. The term "endoscope" generally denotes a class of optical devices used for examining the internal cavities of the human body. The term "borescope" generally denotes a class of analogous devices for examining internal cavities in machinery or other nonhuman areas. Endoscopes and boroscopes, have the same basic structure. Each contains an objective lens for gathering an image, one or more intermediate relay lenses or fiber optics for relaying the image through an elongated tube and eyepiece optics for allowing an individual to view the image directly.
The eyepiece optics in endoscopes and boroscopes generally have a similar basic construction. Typically eyepiece optics include an eyepiece housing with a central cavity for any optical elements required by the eyepiece. Externally the eyepiece housing has a neck portion for attachment to an elongated tube from the endoscope or borescope. A frusto-conical or other conoidally-shaped housing section then flares from its distal end to a proximal end and terminates at a cylindrical peripheral flange portion. During direct viewing, an individual places his or her eye at this peripheral flange portion, that may or may not contain a viewing window.
Eyepieces differ by having diverse diameters and by having specially shaped conoidal or flared housing surfaces. These differences may result from requirements of the optical elements contained in the eyepiece or merely from an aesthetic design consideration. Even frusto-conical or flared housing sections of different eyepiece housings may vary for a given diameter eyepiece among eyepieces supplied by different manufacturers.
In many applications it is highly desirable to connect another device to the eyepiece. These devices may include photographic or television cameras or beam splitters for permitting two or more individuals to view an image simultaneously or to allow one individual to view the image directly while a television camera records the image simultaneously. Sometimes an individual has a preference for an eyepiece of a particular size that differs from the size of the eyepiece associated with the endoscope, borescope or the like. In both situations it is desirable to have an adapter that will attach the eyepiece of the desired size or a coupler that will attach a diverse optical device to an eyepiece associated with the endoscope or borescope. In the following discussion the term "coupler" is meant to include any such coupling devices or adapters.
Several couplers have been proposed for mechanically coupling an optical device to an eyepiece including those disclosed in the following U.S. Pat. Nos.
4,066,330 (1978) Jones PA1 4,305,386 (1981) Tawara PA1 4,318,395 (1982) Tawara PA1 4,740,058 (1988) Hori
The Jones patent discloses an endoscope eyepiece with an opto-mechanical coupler. A spring-biased cam ring mounted on the coupler rotates to retract retaining studs and integral heads radially outward. When the studs are retracted the eyepiece can pass between the heads for connection to or separation from the eyepiece. When the cam ring is released, a spring biases it to a stable position and thereby moves the studs radially inward until the heads engage the flared surface of the eyepiece housing. This action clamps the eyepiece to and centers the eyepiece on the coupler.
The Tawara patent ('386) discloses an endoscope accessory mounting device, or coupler, with a spring-biased cam ring that controls the position of axially aligned, radially extending plate cams. When the cam ring is rotated, the eyepiece can freely pass into or separate from an eyepiece receiving socket in the accessory mounting device. When the eyepiece is located in the socket and the cam ring is released, springs displace the cam ring to its stable position and the cam plates rotate into engagement with the flared surface of the eyepiece thereby to clamp and center the accessory mounting device with respect to the eyepiece.
The Tawara patent ('395) also discloses an endoscope coupler with spring-biased axially aligned cam plates that are biased against a radially acting spring biased plunger. In this coupler the eyepiece snaps into the coupler by driving the cam plates away from a central axis and compressing the springs on the cam plates. When the eyepiece seats in a socket, the springs drive the cam plates against the flared surface of the eyepiece to clamp and center the coupler with respect to the eyepiece. An individual compresses the radially acting, diametrically opposed plungers to move the cam plates to an open position when it is desired to separate the coupler from the eyepiece.
The Hori patent ('058) discloses an optical mechanical coupler with a C-shaped clamping member that is axially displaced from a clamping surface and operated by a locking ring or clamp member. When the clamp member rotates to one extreme position it axially displaces the C-shaped clamping member from the clamping surface. An eyepiece can then be inserted from the side. A reverse rotation of the clamp member displaces the C-shaped clamping member into the eyepiece thereby to clamp and center the coupler with respect to the eyepiece.
Over the years the use of these and other mechanical couplers for eyepieces have led to the establishment of a number of desirable coupler criteria. Specifically, the attachment and separation processes must be simple and be capable of being performed with one hand. It should be possible to rotate the coupler with respect to the eyepiece. The coupler must be easy to clean and, in the case of endoscopes, be easy during use to sterilize. It must be inexpensive to produce, and reliable in use. Further, it should be possible to attach a single coupler to eyepieces of a given nominal diameter having diverse cross-sections or forms through the flared housing portions.
Prior art couplers have exhibited some of these criteria, but not all of them. For example, The Tawara patent ('395) coupler enables one-handed operation. The Jones and Tawara patents permit rotation between the eyepiece and the coupler. However, each of the above-described structures requires the assembly of a large number of components in the form of cam plate studs, springs, rotatable control members, plungers and other elements. These structures are complicated, increase the manufacturing complexity and are subject to failure when debris accumulates in the operative mechanism during normal use, particularly in medical applications. Such couplers can not readily be repaired on site. A customer must maintain an inventory of such couplers or must be capable of operating whenever one of these couplers is at the factory for repair. With particular respect to endoscopes, the sterilization process is complicated because the mechanisms can trap solution making it difficult to assure that all the sterilizing solution has been evaporated or removed. Thus none of these couplers exhibit all the desirable criteria. Moreover, none of these couplers incorporate a simple, reliable structure.